The Search for Extraterrestrial Intelligence (SETI) has been dominated for its first half century by a hunt for unusual radio signals transmitted by an advanced civilization. Writing exclusively in March’s Physics World, Davies, director of BEYOND: Center for Fundamental Concepts in Science at Arizona State University in the US, explains why the search for radio signals is limited and how we might progress.

As Davies writes, “speculation about SETI is bedevilled by the trap of anthropocentrism – a tendency to use 21st-century human civilization as a model for what an extraterrestrial civilization would be like... After 50 years of traditional SETI, the time has come to widen the search from radio signals.”

Questioning the idea of an alien civilization beaming radio signals towards Earth, Davies explains that even if the aliens were, say, 500 light years away (close by SETI standards), the aliens would be communicating with Earth in 1510 – long before we were equipped to pick up radio signals.

While SETI activity has been concentrated in radio astronomy, from Frank Drake’s early telescope to the more recent Allen Telescope Array, astronomers have only ever been met with an (almost) eerie silence. Within the next decade, Frank Drake says that the Earth will go "radio silent" due to the advent of underground fiber optic delivery of Internet and wireless traffic and sateliite transmission that beams its signals back to Earth, rather that out to the Milky Way at large.

Davies suggests that there may be more convincing signs of intelligent alien life, either here on Earth in the form of bizarre microorganisms that somehow found their way to Earth, or in space, through spotting the anomalous absence of, for example, energy-generating particles that an alien life form might have harvested.

“Using the full array of scientific methods from genomics to neutrino astrophysics,” Davies writes, “we should begin to scrutinise the solar system and our region of the galaxy for any hint of past or present cosmic company.”

The image at top of page is a color composite image of the central region of our Milky Way galaxy, about 26 000 light years from Earth. Giant clouds of gas and dust are shown in blue, as detected by the LABOCA instrument on the Atacama Pathfinder Experiment (APEX) telescope at submillimetre wavelengths (870 micron). The image shows a region approximately 100 light-years wide.

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It seems to me that the reason we haven't heard from anyone is that radio, when it comes down to intersteller communication, is totally inadequate. so perhaps there is another medium by which intersteller communication is readily carried out. All we have to do is discover it ...!!!!